Past work has demonstrated that language comprehension ability correlates with general chemistry course performance with medium effect sizes. We demonstrate here that language comprehension's strong cognitive grounding can be used to inform effective and equitable pedagogies, namely, instructional interventions that differentially aid low-skilled language comprehenders. We report the design, implementation, and assessment of such an intervention strategy. Guided by two models of comprehension, we predicted that a multiple pre-testing strategy would differentially aid low-skilled comprehenders in a general chemistry class. We also explored the effect of two question types (multiple choice and elaborative interrogation) on this intervention strategy. A within-subjects, learning-goals driven design was used to build the intervention into two semesters of the course; data generated by this approach were analyzed with hierarchical linear models. We found that the achievement gap between low- and high-skilled comprehenders was partially abated by repeated testing prior to course examinations. We also found that the differential benefits of repeated testing could be accounted for entirely by multiple-choice questions, while elaborative interrogation questions had a statistically significant, but negative, impact. The implication of this work for all levels of chemistry teaching is clear: testing can be used to enhance (not just to assess) student learning, and this act affects different groups of students in different ways.